Like the title said, I miss the previous one but the event
page does not appear in game.

Hello, I think the Chaos Full Gear Set is for the players that missed the previous opportunity to get the Chaos Set. If you already claim your Chaos Full Gear Set in the last Heidel Ball, you will not get it this time.

 

Btw, here's the link for the "Obtain a full Chaos Set!": https://www.world.blackdesertm.com/Ocean/News/Detail?boardNo=2113

 

Hope this helps you. :)